As is known, spinal osteosynthesis devices usually comprise vertebral rods which are rigid and bent so as to adapt them to the anatomy of the considered spinal segment, bone anchorage means formed by screws or pedicle hooks, and connecting elements between these anchorage means and the rods. Sometimes the rods are interconnected by transverse connecting devices.
The bending of the rods in two planes (sagittal plane and frontal plane) is a complex operation difficult to properly carry out outside the patient. When this bending operation is carried out on the patient during the surgical intervention, it is also a difficult undertaking and not free from risk for the patient. Moreover, such devices require a large number of parts which considerably increases the time required for the surgical intervention and renders them costly. Naturally, it is desirable to decrease the length of such surgical procedures to reduce the risk posed to the patient and to accordingly reduce associated costs.
In order to overcome these drawbacks, a system has been proposed in Spanish patent application No. 940 10/5 to Barbera Alacreu, filed May 13, 1994, which comprises a plurality of pins fitted one inside the other in pairs so as to form a kind of articulated chain. These pins are provided with anchorage hooks and are traversed longitudinally by a cable for maintaining the assembly under tension in the desired position. When the cable is put under tension, the pins are locked together by friction.
However, such a device has various notable drawbacks. For example, it requires a very high tension to obtain a good adherence or grip between the surfaces in contact. Further, the cable must be fixed at its end by a setting or forming-over operation which requires a high degree of skill to effectively carry out in the operating theatre. Lastly, in the event of breakage of the cable, the assembly of the pins is no longer maintained and the device collapses, which is a particularly serious risk for the patient.
Thus, there is a need for a spinal stabilization system that may be more readily shaped to conform to desired contours in the sagittal and frontal planes. Preferably, such multidimensional shaping may be easily performed and still provide a rigid stabilization construct once the desired shape is attained. The present invention meets these needs and has other significant advantages and benefits.